1. Field of the Invention
The present invention relates to a new and improved dewatering device for the web-forming or wet section of a papermaking machine.
Generally speaking, the dewatering device for the web-forming or wet section of a papermaking machine according to the present invention is of the type comprising foils or strips or ledges disposed transverse to a predetermined direction of travel of the forming wire or sieve, that is to say, the foils extend in the cross-machine direction. These foils are individually adjustable or else adjustable in groups or sets in the direction of the forming wire. Through the use of force or powering elements for the foils there can be exerted, by means of the foils, a predetermined or desired force or pressure action upon the forming wire, especially for the dewatering and formation of the paper web or sheet formed of fiber stock suspension which is located upon the forming wire.
2. Discussion of the Background and Material Information
Dewatering devices of this type can be constructed, for instance, in the manner disclosed in the commonly assigned German Patent Publication No. 3,929,265, published Mar. 28, 1991. This published German document teaches the possibility of rendering foils individually adjustable, in order to be able to adjust or set their position and to exert a force upon the forming wire as a function of prevailing requirements. Depending upon the operating conditions under which these foils are used, particularly when there are required considerable adjustment distances through which the foils must be moved, it can happen, however, that these foils experience undesired seizing and bending. One of the main reasons that this occurs is attributable to the fact that frictional forces arise at the location where the foils come into contact with the traveling forming wire. By virtue of the prevailing lever action these frictional forces produce a moment which must be taken up by the guides of the foil adjustment mechanism, and hence, there can result the aforenoted foil seizure or binding and foil bending. Since at this location of the papermaking machine high precision settings and regulation operations must be carried out, appreciable drawbacks arise during the manufacture of high-quality paper sheets or webs when the foil adjustment mechanism operates inaccurately.
Other dewatering devices are also known in this technology wherein a multiplicity of foils or ledges are mounted at a frame and this frame can be pressed against the forming wire of the papermaking machine through the use of appropriate force or powering elements. While such systems can be rather easily constructed such that the foils do not seize or clamp, nonetheless there is here not possible individual adjustment or setting of the foils.